Effect of Urea and Ammonium Sulfate on Growth Rate, Net Assimilation Rate and Leaf Area Index of Aromatic Rice cv. Pathumtani 1

Abstract

Rice (Oryza sativa L.) cv Pathumtani 1, a newly aromatic variety, has not well understood in the physiological response of nitrogen fertilizer. In this study, 2 types of nitrogen fertilizers; urea and ammonium sulfate at 0, 10, 20, 40 and 80 kilograms N/rai was conducted to investigate growth rate, leaf area index (LAI) and net assimilation rate (NAR) of rice cv Pathumtani at 3 phases of growth; vegetative (31 —51 days after transplanted), reproductive (51—79 days after transplanted) and ripening (79—100 days after transplanted). Rice was grown in pot containing of sand added modified Hoagland’s solution (without any nitrogen source). The results showed that ammonium sulfate could enhance growth rate, LAI and NAR of rice than those using urea fertilizer. However, rice grown in the solution contained nitrogen lower than 20 kilograms N/rai resulted in a stunt growth, dwarf shoot, pale green to yellow or brown of older leaves. In contrast to the treatment using 80 kilograms N/rai, the rice had a large number of leaves, dark green leaves, and aborted seed. The final results showed that rice using ammonium sulfate at 20 kilograms N/rai could have not only maximum at vegetative phase but also resulted in a highest average yield. It could he concluded that the physiological responses to nitrogen fertilizer of aromatic rice cv Pathumtani 1 has a greater response in vegetative phase and ammonium sulfate fertilizer also has a higher response than those urea. Thus, the recommendation for using nitrogen fertilizer of aromatic rice cv Pathumtani 1 will be applied ammonium sulfate after transplanting in order to get the highest growth and average yield.